A cobporation of pennsyl



I. B. SMiTH. OPHCM. PYROMETRY" nrmcmon min m1. 6. m9.

Patented" 0%.,28, 1919.

UNITED STATES PATENT on uon.

IRVING B. SMITH, 0F AMIBLER, PENNSYLVANIA, ASSIGNOBHTO LEEDS & NORTHRUP COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYL- VANIA.

OPTICAL PYROMETB-Y.

Pate ntedpct. 28, 1919.

Application filed A ril a, mic. Serial m. cacao.

To all whom. it may concern:

Be it known that I, IRVING B. SMITH, a citizen of the United States, residing in Ambler, State of Pennsylvania, have invented certain new and useful Improvements in Optical Pyrometry, of which the following is a specification.

My invention relates to optical pyrometry wherein an electric current passed through a light standard, as an incandescent lamp, is varied until the brightness of that standard matches the brightness of the incandescent body whose temperature is to be determined. 7

In optical pyronietry of the character referred to it has been customary to measure the current passed through the lamp standard by a DArsonval or other suitable ga1- vanometer calibrated in units of temperature or units of current, as milliamperes, the galvanometer being connected in series with the light standard or incandescent filament. .W'ith such an arrangement the useful part of the scale of the instrument is comparatively short or cramped.

I have found that while such a mode of connection of the measuring instrument or galvunometer may be suitable for an incuildcseent lamp filament of carbon or other material of negative temperature coeiiicient, when tungsten or other filaments having positive temperature coefficient are emp r ved, a far better instrument scale is available if the galvanometer be not emalo ved in an amineter or series relation, but be employed in a voltmeter 0r shunt relation.

y employin the galvanometer as a voltmeter or mil lvoltmeter connected in shunt to the tungsten or other lamp filament having positive temperature coefficient or in other analogois arrangement, an extended scale is procurable which obviously is an advantage in making readings, as of temperature, because an extended or longer scale can be read with correspondingly greater degree of refinement and accuracy.

My invention will be understood to reside therefore in an arrangement of the character referred to wherein the galvanometer is employed as a voltmeter connected in shunt to the lamp filament, or in analogmis relation.

For an illustration of some of the various forms my invention may take, reference is to be had to the accompanying drawing, in which: v

Figure 1 is in part a cross sectional view optical pyrometric apparatus and in part a diagrammatic view of circuit arrangement.

Fig. 2 is an illustration of the scale of a. galvanometer employed in the series or current measuring relation.

Fig. 3 is an illustration of a scale resulting rom my new mode of connection.

Fig. 4 is a diagrammatic view of modified circuit arrangement coming within my invention.

Fig. 5 is a diagrammatic view of 'a further modification of circuit arrangement coming Within m invention.

Referring to i. I, 1 is a tube upon which telescopes t e tube 2 having at its front end the objective lens 3. The tube 1 is closed at its rear end by the member at supporting the eye piece structure having the ocular lens 5 in front of which are disposed suitable lass screens 1* and of red or other suitably colored glass. uitably disposed within the tube 1 is the incandescent lamp L havingv the filament F whose terminals, respectively,are connected to the lamp base terminals 16 and 17, to which are connected, preferably by soldering, conductors constituting leads of low or suitable resistance connect' to the terminals of the galvanometer V. 'Ehe lamp filament F is in. series with the battery or source of current 76 and the variable resistance or rheostat Between the lamp L and the objective 3 is disposed the member or diaphra 1 9 having the aperture 10 in the optica axis of the instrument, in which axis is o the aperture 11 adjacent the eye piece st ture. Upon the member 9 is pivoted at 12 the the exterior of the telescope structure. At its inner end the lever 13 cerriesthe holder 14, in which are disposed absorption screen elements of any suitable character, as G and P. i

Assuming the absorption screen structure (1 P shifted to one side of the optical axis of the instrument, and further assuming the Q lever 13 having a handle 14: extending'to A nected in series with the lamp filament milliamperes or directly in temperatures on a scale of the character indicated in Fig. 2. This scale, graduated in temperatures ranging from 1200 to 2500 degrees Fahrenheit,

usually the range for the filament F., will be seer. to be relatively short when considerin the entire arcuate length of the scale whic corresponds to the available deflection of a DArsonval galvanometer.

By connecting the galvanometer as a voltmeter V, as in Fig. 1, in shunt to the tungsten or other filament F of positive temperature co-eflicient a scale of the character shown in Fig. 3 is available for the same range of tem eratures. with both scales, igs. 2 and 3, the same galvanometer and same filament F are as sumed. For a temperature of 2500 degrees, Fig. 2 550 milliamperes, for example, flow through the moving coil of the instrument. In the case of Fig. 3, however, at 2500 degrees Fahrenheit, the fall of potential across the same filament F is for example,

cal

Cal

ing materially longer than the scale of Fig.-

2 for the same range of temperatures. Fig. 3 is a scale which is more open or extended than the scale of Fig. 2 and is more readily utilizable for greater refinement and accuracy in readings.

A scale of the character of Fig. 3 is available when the lamp filament F is of lung sten or other metal or material having a suitably high positive temperature coeflicient, for in such case the voltage drop across its terminals rises more rapidly than the current strength .therethrough.

It will be understood that a pyrometer of the character referred to with the voltmeter connection described may have a second range scale, as well understood in the art, when an absorption screen structure, as G, P, is in position indicated in Fig. l for absorbing some of the light transmitted. from the imandescent body whose temperature is to be measured. But such second or high range scale will have the same general character istics as the scale of Fig. 3 referred to, be-

In connection,

cause the lamp filament temperature and currents are of a range the same as m the ,case where the absorption screen is absent.

While thcitnode of connection shown in Fig. 1 is my preferred arrangement, namely, the voltmeter connected directly across the terminals of the lamp filament, an arrangement such as shown in Fig. 4 may be employed wherein 15 is a resistance in series with a lamp filament F of any suitable character, such resistance 15 having any suitable structure or nature, but having a substantial or high positive temperature coefficient. In fact, the resistance 15 may be a lamp filament of tungsten or other suitable material, or a fine iron wire incloscd in a nonoxidizing atmosphere or vacuum. In this case, the same current traversing the filament F traverses the resistance 15, which will be so heated by the current that its resistance rises quite rapidly, so giving a fall of potential at its terminals, so measured by voltmeter V that a: scale of a similarly open or extended character of Fig. 3" is obtainable.

In Fig. 5 the resistance 14"), which may be of the same character as described in connection with Fig. 4, is again in series with a lamp filament F, but the voltmeter V is connected both in shunt to the lampfilamerit I and resistance 15. Here again a 'scale of the general character of Fig. 3 is obtainable.

That I claim is:

1. Optical pyrometric apparatus compris ing a circuit including a light standard, a. source of current therefor, means for varying the current in said light standard, a part of said circuit having a positive temperature coefiicient. whereby the potential drop across said part increases at a rate greater than the rate of increase of current in said light standard, and a galvanometmemployed as a voltmeter connected in shunt to said part of said circuit having a positive temperature coefficient.

2. Optical pyrometric apparatus comprising a circuit including a light standard, -a.

source of current therefor, means for varying the current in said light standard, a"

a positive tempart of said circuit having) h y t e potential perature cocfiicient, where drop across said part iicreases at a rate greater than the rate of increase of current in said light standard, a galvanometer emplo ed as a voltmeter connected in shunt t0 in temperature a source of current therefor, means for varying the current strength in said member, and a galvanometer employed as a voltmeter connected in shunt to said member.

4. Optical pyrometric apparatus comprising a circuit including atungstenfilament, a source of current therefor and means for varying the current strength in said filament, a galvanometer connected in shunt to a part of said circuit includin said filament, said part of said circuit having as a whole a posltive temperature coefiicient, and a scale for said galvanometer graduated in temperature units.

5. Pyrometric apparatus comprising a circuit including a lamp filament having a: positive temperature coeflicient, a source of current therefor and means for varying the current through said" filament, a galvanometer employed as avoltmeter connected in shunt to a part of the entire resistance of said circuit having a positive temperature coeflicient, and a scale for said galvancmeter calibrated in temperature units.

6. Optical pyrometric apparatus comprising a circuitlmcluding a lamp filament having a positive tem rature coeificient, a

source of current an means for var ing the current in said lamp filament, a ga vanomtemperature units.

eter connected in shunt to a art of said circuit inicludin said lamp lament, and a scale for sai galvanometer calibrated in current in said filament, and a galvanometer connected in shunt to said lamp filament.

8. O tical pyrometric apparatus complrising a circuit including a lamp filament aving a positive temperature coefiicient, a source of current and means for varying the current in said filament, a galvanometer connected in shunt to said lamp filament, and a scale for said galvanometer calibrated in temperature units.

9, Pyromctric apparatus com rising a circuit including a metal lamp filament, a source of current and means for varying the current in said filament and a DArsonval galvanometer having a scale calibrated in temperature units connected in shunt to said filament.

In testimony whereof I have hereunto aflixed my signature this 7th day of April,

IRVING B. SMITH. 

